1. Field of the Invention
The present invention relates to an interlock device of a ring main unit, and more particularly, to an interlock device of a ring main unit in which a fuse cover can be closed in interlock with a cable cover.
2. Description of the Related Art
In general, as a device used to monitor, control and protect an electrical system configured to transmit and distribute power sent to customers through transmission and distribution, ring main unit (RMU) may be configured with an assembly of a circuit breaker, a switchgear, grounds and conductors within a structure that is sealed and insulated by SF6 gas.
A ring main unit according to the related art is illustrated in FIG. 1, and a configuration in which a fuse cover and a cable cover are removed from the configuration of FIG. 1 is illustrated in FIG. 2. A fuse cover 2 and a cable cover 3 are provided on a front surface of a ring main unit 1, and various apparatus such as a circuit breaker, a switch, a disconnecting switch, an earth switch and the like are housed within the ring main unit 1 and interlock devices are provided therein to control their operations.
Among those interlock devices, an interlock device implemented in the fuse cover 2 has two types of functions. The first function is a function to allow the opening of the fuse cover 2 only when in a ground state in connection with an operating mechanism of the relevant circuit. The second function is a function to allow the opening of the cable cover 3 only in a state that the fuse cover 2 is open when both the cable cover 3 and fuse cover 2 are mounted thereon. Through this, the fuse cover 2 may be allowed to be open only when an operating mechanism of the relevant circuit is in a ground state, and the cable cover 3 may be also allowed to be open only in a state that the fuse cover 2 is open.
Furthermore, an interlock device for interlocking the operating mechanism of the relevant circuit with the fuse cover 2 may be also applied not to operate the relevant operating mechanism in a state that the fuse cover 2 is open.
However, when both the fuse cover 2 and cable cover 3 are open and then the fuse cover 2 is closed while the operating mechanism of the relevant circuit is in a ground state, the operating mechanism of the relevant circuit will be in an always operable state. In this case, the relevant circuit will be in an always-on state, and thus there is a risk of accident such as dielectric breakdown due to contact when a person approaches a cable portion through which electricity flows in an active state.